Manifest Destiny and the Mexican War

In the 1840s many Americans
supported expansion of the American nation. They believed in a concept
known as Manifest Destiny. Manifest Destiny is the idea that it is
the destiny of the United States to expand American democracy and liberty
over the entire North American continent, or at least from the Atlantic
Ocean to the Pacific Ocean.

In 1846 the United States
went to war with Mexico, partly over the issue of
annexing Texas. Texas, once a part of Mexico, had declared its independence
as a republic, but wanted to be a part of the United States. Mexico
feared that making Texas a part of the United States would lead to the
loss of more Mexican territory in the future. For many Americans
who supported annexation, adding Texas to the United States was a fulfillment
of Manifest Destiny.